Canister purge valves are used to prevent evaporated fuel, in particular hydrocarbons, from escaping into the atmosphere. For this reason, an activated carbon canister is connected to the fuel tank. The canister is able to retain the fuel that has evaporated from the tank. For this reason the fuel tank is ventilated only through the filter. However, the activated carbon container provides only a limited holding volume. Consequently, the activated carbon must be continuously purged. To this end, the running engine takes air through the filter that is supplied as a combustion mixture to the motor. To maintain the exhaust emissions within statutory limits and to ensure favorable engine running conditions, the supply of the regenerating mixture of air and fuel vapor from the activated carbon filter to the engine is controlled. The canister purge valve is thus opened or closed by the purge valve so that the desired purge is timed through an adjustment of the engine characteristics, for example, according to the load and rotational speed parameters. Usually, the purging of the active carbon filter is deactivated in specific operating ranges. This, for example, occurs during idle time and under full load. The latter results from the lack of vacuum in an intake manifold of the motor, so that no regenerating mixture of air and fuel vapor can be drawn off from the activated carbon. Furthermore, a lambda control can be engaged to adjust the flow volume of the regenerating mixture of air and fuel vapor to the desired exhaust emission performance of the engine.